1. Field of the Invention
This disclosure relates to a liquid crystal display (LCD) device, and more particularly to an LCD device adapted to reduce power consumption and to prevent deterioration of the picture quality and to a method of manufacturing the same.
2. Discussion of the Related Art
The current trend is that liquid crystal display (LCD) devices are widening their application in various fields because of their features, such as their light weight, slimness, low driving voltage, and so on. This trend is evidently confirmed in the ways in which the LCD devices have been applied to office automation equipment, audio equipment, video equipment, and so on.
LCD devices adopt a light transmittance characteristic of liquid crystal varying along an applied voltage and convert electric signals into visual information, thereby displaying an image. The liquid crystal should be of a material which is in a medium state between the liquid and the crystal. To this end, the LCD devices each include two substrates having electrodes and a liquid crystal layer interposed between the substrates. Such LCD devices are lighter and thinner and are driven at a lower voltage in comparison with other display devices that have the same screen size.
The LCD device allows each pixel of an LCD panel in its front side to selectively transmit light emitted from a light source in its rear side, thereby displaying an image. In this case, each pixel on the LCD panel functions as a light switch. Such an LCD device controls the intensity of light generated in the light source so as to display an image, unlike a CRT (Cathode Ray Tube) of the related art which adjusts the intensity of an electric beam and controls brightness.
The LCD panel included in the above mentioned LCD device is manufactured in a structure in which a color filter substrate (i.e., an upper substrate) and a thin film transistor substrate (i.e., a lower substrate) are combined with a liquid crystal layer between the two substrates. The color filter substrate is provided with color filters formed thereon. The thin film transistor substrate is provided with thin film transistors formed thereon.
The thin film transistor substrate of the ordinary LCD panel includes gate lines and data lines crossing each other and thin film transistors TFTs formed at intersections of the gate and data lines.
Each of the thin film transistors includes a gate electrode and source/drain electrodes formed with a gate insulation layer between the electrodes. The drain electrode is electrically connected to a pixel electrode.
A passivation (or protective) layer is formed on the gate insulation layer provided with the source/drain electrode and the pixel electrode. A common electrode wiring and a common electrode pattern are formed on the passivation layer.
In this manner, the thin film transistor substrate included in the ordinary LCD device of a transverse electric field mode forces not only the common wiring to be formed on the gate and data lines but also the common pattern to be formed on the pixel electrode. As such, a parasitic capacitance is caused between the gate and data lines and the common electrode wiring, and furthermore a vertical crosstalk occurs. Therefore, picture quality of the ordinary LCD device deteriorates.
In order to reduce the parasitic capacitance, the ordinary LCD device can be designed to increase the thickness of the passivation layer. In this case, the distance between the pixel electrode and the common electrode patterns must be enlarged. As such, the transmittance characteristic of the ordinary LCD device is lowered due to the decrease of the electric power affecting the electric field which is applied to the liquid crystal. Also, it causes difficulties in the manufacturing process of the LCD device. Furthermore, the WVGA (Wide Video Graphics Array) LCD device of a high definition model having 800×400 dots forces a storage capacitance between the pixel electrode and the common electrode pattern to decrease due to its small-sized pixel.